Endodontic instrument

ABSTRACT

An endodontic file, for manual or motor driven use by an endodontist, includes a color-coded handle, a shank, and a serrated cutting edge. The cutting edge of the endodontic file is side-cutting with pyramidal teeth and ends in a pointed tip. The endodontic file is used manually inside the root canal in an “up and down” axially aligned motion and these pyramidal teeth will provide a ripping action. A second type of endodontic file has a curved cross section and a sharpened tip. with pyramidal teeth lining the edges of curved blade section. A third type of endodontic file has a flat debriding side which tapers to a point; with a series of adjacent 3-D pyramids emerging from this surface for removing loose material or in urging already loosened material from a root canal.

FIELD OF THE INVENTION

The present invention relates to hand-held and mechanized endodonticretreatment files which can be used in endodontic re-treatments, as wellas in original root canal treatments.

BACKGROUND OF THE INVENTION

Successful root canal treatment depends on adequate debridement andfilling of the entire root canal system. Failure to recognize thepresence of an additional root canal, adequately remove the pulp tissue,and disinfect and obturate the root canals properly, may cause thefailure of the entire treatment. Therefore, it is important to befamiliar with the variations in the root canal morphology because suchknowledge can help in the location and negotiation of the canals as wellas proper subsequent intervention of using the right root canalinstrumentation to create a tapered shape with adequate volume to alloweffective irrigation and filling.

Many instruments, devices and instrumentation techniques have beenrecommended but only few seem to be capable of consistently achievingthese primary objectives of root canal preparation. Methods ofmechanical preparation include manual preparation using K and H handfiles, ultrasonic instrumentation, and automated rotary systems (e.g.Protaper, D-race, MTwo-R):

-   -   Proper biomechanical cleaning and shaping of root canals        requires the use of stainless-steel hand files with the increase        of stiffness in larger instrument sizes that may cause several        mishaps, such as ledges, zips, perforation and root canal        transportation. This was replaced by rotary instruments which        possess advantageous bending and torsional properties attributed        to their low modulus of elasticity but are prone to fracture and        provide less than optimum cleaning efficiency of the root canal.    -   Neither of the hand or rotary endodontic instruments currently        on the market can provide complete debridement or removal of        existing obturating material.

Another problem associated with using spiral fluted shaped endodonticfiles is that they tend to have a diameter that is larger than thethickness of the gutta percha material surrounding a plastic “carrier”core that replaces the removed human tissue pulp and nerves of theoriginal root canal treatment. The carrier core can place increasedtorsional fatigue on the spiral endodontic file instrument, requiringlonger time to remove the coagulated gutta percha material surroundingthe plastic carrier core, or can damage the spiral endodontic fileinstrument itself.

The torsional fatigue problem is an industry wide problem in endodonticre-treatments. Scholarly literature documents attest to these problems.

For example, Nevares, et al, in Gutta PerchaCore More Easily Removedfrom the Root Canal Than Thermafil? An ex-vivo study, J Can Dent Assoc2015; 8:f22 notes that the use of ProTaper retreatment files is anefficient method for removing filling material, but this technique alonemay not suffice. As noted in Neveras, et al, “In the present study,retreatment time for the samples filled with Thermafil was significantlylonger than for those filled with GuttaCore or continuous wave ofcondensation (control group). In 2013, Beasley et al and others alsoobserved longer retreatment time with Thermafil compared with GuttaCore. However; despite the significant difference, this may not berelevant clinically. The increased time required was attributed togreater difficulty in removing the plastic carrier. According to Wilcox,30 “Adequacy of Thermafil retreatment may be related more to the abilityto easily remove the carrier than to the technique of gutta-percharemoval.”

Beasley, et al, in Time Required to Remove GuttaCore, Thermafil Plus,and Thermoplasticized Gutta-percha from Moderately Curved Root Canalswith ProTaper Files, Journal of Endodontics, Volume 39, Number 1,January 2013, notes that Thermafil carriers may increase the ease andefficiency of obturation, but in the event of failure, their retreatmentadds a layer of complexity to treatment decisions. The tendency ofProTaper Retreatment files to unwind and separate that was found in thisstudy may be related to the taper of the ProTaper Retreatment files (15,35) or the speed at which they rotate in curved canals (13). Theseevents occurred more frequently in the Thermafil group, which may beattributed to the increased torsional fatigue placed on the instrumentsby the plastic carrier.

Besides the use of rotary instruments to grind away gutta perchasurrounding dense, hard plastic centrally located carrier cores in aroot canal re-treatment procedure, practitioners normally tend tocombine multiple means together, i.e, initiate re-treatment with rotaryfiles, irrigate with solvents, use rotary and hand file alternately andapply some heat as well.

As of now, all these techniques have shown some success in re-treatingregular root canal treatments filled only with gutta percha, but not themore recent carrier-based re-treatments, which is the targeted subjectmatter of this present application.

For example, the use of heat as in “System B Heat Source” in trying toremove gutta percha in a previously treated root canal can cause injuryto the periodontal ligaments. For example, Lipski, et al., in In VitroInfrared Thermographic Assessment of Root Surface Temperature RisesDuring Thermafil Retreatment Using System B, Journal of Endodontics,Vol. 29, No. 6, June 2003, notes that Thermafil retreatment using SystemB Heatsource plugger inserted for 5 seconds generated temperature risesthree times higher than permissible. As expected, the temperature risewas higher when the plugger placement time was increased to 8 seconds.

Because the possibility exists that periodontal structures including theperiodontal ligament, alveolar bone, and vasculature could insulate andprotect the periodontal unit from damaging temperature rises, this studyshould be performed in an in vivo model. Meanwhile, endodonticpractitioners should exercise caution when using the System B techniqueto retreat Thermafil obturated teeth. More importantly, Lipski, et al.,noted the inherent problems for the patient if elevated heat were used.Lipski, et al., stated: “It is generally accepted that a 10° C.elevation in temperature on the root surface, to approximately 47° C. ispotentially damaging to the cementum, periodontal ligament, and alveolarbone” citing Eriksson A R, Albrektsson T. Temperature threshold levelsfor heat-induced bone tissue injury: a vital microscopic study in therabbit, J Prosth Dent 1983:50; 101-7, Saunders E M. In vivo findingsassociated with heat generation during thermomechanical compaction ofgutta-percha. Part II. Histological response to temperature elevation onthe external surface of the root. J Endodon 1990:23:268-74, Lipski M.The temperature rise on the outer root surface during root canal fillingby Thermafil obturators. Magazyn Stomat 1999; 9:28-31.

Both solvents and heat are regularly used in endodontics but owing totheir side effects, their usage should be limited to the minimum and inspecial situations only. For example, in Duncan et al, Removal of rootfilling materials, Endodontic Topics 2011, 19, 33-57, an article thatexplains different methods of removing gutta percha, solvents aredescribed as being useful for dissolving gutta percha, but that mostsolvents are questioned for being cytotoxic and studies are looking formore safer ones. With respect to chloroform as a solvent for dissolvinggutta percha, Duncan et al states at page 39 “However, concerns havebeen raised regarding its cytotoxicity if it comes into contact withperiapical tissues; it has been classed as a carcinogen and a potentialrisk to the dental team.”

Alhashimi, et al, An In Vitro Assessment of Gutta Percha Coating of NewCarrier-Based Root Canal Fillings, Scientific World Journal, Vol. 2014,article ID 239754, 6 pages, notes that root canal treatments includeinsertion of approximately 25 mm length carrier cores, each havingthicknesses of about 0.60 mm+/−0.02 mm to about 0.66 mm+/−0.04 mm atpredetermined cross sectional areas. It is also noted that these carriercores are surrounded by gutta percha material. Alhashimi et al measuredthe thickness of gutta percha surrounding the carrier at four points,representing 12 o'clock, 3 o'clock, 6 o'clock and 9 o'clock along thecircumference of the gutta percha at designated portions of the carriercore. In one example, the thickness of the gutta percha materialsurrounding the carriers having respective thicknesses of 0.60 and 0.66mm, where the gutta percha at the four designated clock locations hadthicknesses of 0.376 mm+/−0.027 mm at the top, 0.164+/−0.023 at the 3o'clock location, 0.357 mm+/−0.033 mm at the six o'clock designation and0.591 mm+/−0.034 mm at the 9 o'clock peripheral location.

Therefore, according to Alhashimi, et al, the thickness of gutta perchavaried from about 0.164 to about 0.591 mm in thickness between thedentin and the outer surface of the carrier core.

Consequently, in re-treatment procedures, it is necessary to cut intothe gutta percha surrounding the carrier core. The problem with typicalspiral rotary endodontic files with spiraling fluted surfaces is that attheir respective distal ends, the initial outer diameter at the distalend may be 0.19 mm/mm, but it increases in outer diameter to about 1.2mm/mm at the top proximal end, as in the endodontic files of ProTaperShaping file X. It would be difficult to use the tapered endodontic filethat widens to 1.2 mm/mm for trying to dig into and remove gutta perchahaving diameters of about 0.376 mm, 0.357 mm or 0.591 mm, as discussedin Alhashimi, et al, since much of the spiral endodontic file could besignificantly in excess in diameter of the gutta percha material soughtto be removed. Therefore, it would be a tight squeeze to insert atypical spiral rotary endodontic file into the thin gutta perchamaterial surrounding the resistant plastic carrier core.

Brown, in Retreatment of Thermafill Carriers, Tri City/FallbrookMicroendodontics, 2018, discloses that retreatment of Thermafil Carriersis difficult because the metal or plastic carriers are dense, so thatpenetrating them is “tough and/or impossible.” Brown also discloses the“Braiding Technique” by inserting a plurality of H-Files into the canaladjacent to the carrier to bind it to the H-Files and remove it. Butfirst the adjacent gutta percha material must be removed by solvents orgrinding down into removable pieces.

Prior art also reveals several options for implementing a poweredendodontic spiraled fluted handpiece. W & H DentalWerks of Germanydescribes a motor driven handpiece for cutting jaw bones, which may beadapted for orthodontic rework. Their S-8 series supports sagittal,oscillating, or reciprocating movement. U.S. Pat. No. 8,910,727 ofBar-Cohen, et al. for an ultrasonic/sonic jackhammer is one approachthat would involve miniaturization of the construction tool described;rotation would have to be added. U.S. Pat. No. 4,353,698 of McSpaddenhas an electric motor driven power head for a rotary drive to compact GPin initial root canal procedures. U.S. Pat. No. 10,383,702 of Levydescribes an angle piece head that actually imparts both rotary as wellas angled mechanical impulses. U.S. Pat. No. 5,770,913 of Mizzi and U.S.Pat. No. 6,069,420 of Mizzi, et al., for specialized actuators driven byoscillatory transducers are involved with linear as well as rotarymotors that can use a wide variety of prime movers including electric aswell as pneumatic elements.

OBJECTS OF THE INVENTION

A new endodontic file with side cutting-edge and a flat cross section isdescribed. The cutting edge has pyramidal teeth (hence the tradenameP-file) which are shaped in a preferred embodiment as an isoscelestriangle.

The P-file aims to provide a cutting alternative for cleaning andshaping as well as retreatment of the root canal.

It is therefore an object of the present invention to re-treat aprevious but damaged root canal treatment by removing a centrallylocated carrier, (i.e. “core”), surrounded by a sleeve of gutta percha,which is done in an indirect way by removing the gutta percha, withoutdamaging the carrier, then the carrier can be easily removed withoutdamage to the carrier or to the surrounding dentin of the patient's rootcanal needing re-treatment, due to new infections or trauma, resultingin structural damage to the original tooth and/or post, core or crown ofthe patient's tooth.

The new endodontic “P-file” aims to provide a new cutting alternative tocurrent protocols of cleaning and shaping as well as re-treatment ofroot canal system. The file is more efficient, saving time and posesfewer side effects on the tooth structure.

It is also an object of the present invention to be able to provide athin saw teeth endodontic file, which is sharp enough and thin enough todig into and remove gutta percha material separating the centrallylocated, hard plastic carrier core in an endodontically treated rootcanal from the patient's teeth. This emphasizes the fact that the narrowcross-section of the cutting teeth of the endodontic file of the presentinvention is critical to the main concept of the endodontic file and thefact that this is a unique design not manufactured before.

Other objects will become apparent from the following description of thepresent invention.

Retreatment of prior root canal treatment is important in endodontics.In the event the re-treatment is not done properly, the only options thepatient will have are surgical re-treatment or extraction. Medicalconditions and cost can prohibit patients from doing surgicalre-treatment and they opt for extraction of the tooth. Hence, theultimate goal of this new file design is to save teeth from extraction.

According to the American Association of Endodontics, in its websiteinformation about endodontic re-treatment, it is noted that “with propercare, even teeth that have had root canal treatment can last a lifetime.But sometimes, a tooth that has been treated doesn't heal properly andcan become painful or diseased months or even years after treatment. Ifyour tooth failed to heal or develops new problems, you have a secondchance. An additional procedure may be able to support healing and saveyour tooth. If you have pain or discomfort in a previously treatedtooth, talk to an endodontist about retreatment.”

SUMMARY OF THE INVENTION

In keeping with these objects and others which may become apparent, thepresent invention is a new endodontic file, the P-file, which, formanual use by an endodontist, includes a color-coded handle, acylindrical or preferably cuboid shaped shank, and a cutting edge bladewith a linear array of adjacent saw teeth. The endodontic file isdesigned to follow the ISO standardization with a size of 15-45 mm. TheP-file is made of stainless steel or Ni—Ti (nickel titanium) using a 3Dlaser cutting machine, wire machining or CAD/CAM milling. The cuttingedge of the endodontic file is side-cutting with pyramidal teeth andends in a pointed tip. The P-file is to be used manually inside the rootcanal in an “up and down” axially aligned motion and these pyramidalteeth will provide a ripping action.

A second type of endodontic file has a curved cross section and asharpened tip. It is shaped roughly as a “vegetable corer” withpyramidal teeth lining the edges of blade section. It is designed to beused manually with a handle in an up & down motion while cutting ineither side that is forced against the material to be removed duringdebridement of either initial or retreatment procedures. Preferably thecorer's C-shaped cross section has an inner radius of curvature slightlylarger than the outside diameter of the carrier core in the tooth canalbeing retreated, so it fits easily in the annular gutta percha spacebetween the carrier core and tooth dentin. In an optional embodiment thesaw teeth denticular projections can also be on the sharp distal end,instead of being a continuous curved sharp blade. Alternately, thelocation of the saw tooth denticular projections can be on any portionof the portion. With teeth on the bottom distal edge, the corer can be a“starter tool” for retreatment in the top (proximal region) of a toothcanal. The endodontist would set it around the core and rotate it byhand to cut through the top portion of the gutta percha annular ringnear the top of the tooth canal being re-treated.

A third type of endodontic file has a flat debriding side which tapersto a point; a series of adjacent 3-D pyramids emerge from this surface.This is used as aid in removing loose material or in urging alreadyloosened material from a root canal.

Other embodiments involve the use of file teeth with different profilesas well as files with teeth on both edges.

In an alternate embodiment, the teeth may be other than isosceles equalsided triangles. For example, they could have a side cutting surface atany amount and then a vertical surface adjacent to and extending downfrom the apex of the angled surface.

They can also be an alternate embodiment, have equal sided triangles,but not isosceles, so that they would have less of an angle, but beequal.

Another embodiment would be where one of the sides of the triangle wouldbe longer than the other, so that it would have less of an angle thanthe adjacent side.

In addition, in certain embodiments, the triangles of the saw teeth atthe valleys, between adjacent saw teeth triangles, will be rounded offso that it is easier to make than to just have them both converge topoints in the valleys between the adjacent saw teeth triangles, so thatthere will be a concave cavity at the bottom.

In another embodiment, instead of having a cylindrical shank holdingportion for the cutting blade of the endodontic file for treatment inthe root canal, the shank can have a cuboid or boxlike shape, withperpendicular sides and top and bottom, which is stronger to support thesaw teeth blade. Cuboids are convex polyhedrons which have six faceswith edges, where adjacent faces are perpendicular to other adjacentfaces of the polyhedron.

In another embodiment, the endodontic file can optionally haveparabolic-shaped saw teeth adjacent to one another, where instead oflinear sides extending upward towards an apex point, the sides would beextending upward and converging towards a tangent to a curve, as in aparabola.

Therefore, in general, the saw teeth comprise two or more linear sidesconverging to a top apex point or region. When the converging sides arelinear converging to an apex, the shape of each saw tooth is that of atriangle, either equilateral or non-equilateral. If the converging sidesare curved and arcuate, converging to a curved apex, then the shape ofeach saw tooth of the blade is that of a parabola, or one half of aninverse parabola.

In some cases, when viewed from the top, there will be the linearportions of the cutting edges, will extend side to side, but less of awidth than the blade supporting portion, which extends from the shank,so that when viewed from an end view, it would be a trapezoid, where thesmaller portion on top would be the cutting surface and the wider bottomportion would be the bottom of the blade support portion In thatversion, both the teeth and the blade support portion would becoterminous with each other, with no joints, although extending slantingupward as in the sides of a trapezoid.

Another situation would be when the gutta percha is in the root canaland it is failing and must be removed, The gutta percha is normally aseal around a hardened, plastic carrier core, so that if one uses solespiraling endodontic files, they will not work, because they will getresistance when contacting the essential core carrier, which issurrounded by the gutta percha material, which can be removed with thesaw teeth. Therefore, in the present invention, the saw teeth arecutting on a surface and they can easily be manually or motor driventhrough the surrounding circumferential gutta percha, which surroundsthe exterior surface of the core carrier, which cannot be done with aspinning, fluted, spiraling endodontic file.

Therefore the main goal of the endodontist in re-treating this kind ofobturation material (carrier-based obturation materials) is to maintainthe carrier as intact as possible for easy retrieval and by using thethin saw-blade teeth and thin cross-section of the cutting part, thefile can fit between the carrier and the dentin wall ripping through thegutta-percha without potentially damaging the carrier core which issomething the rotary files can't do owing to their roundedcross-section.

This emphasizes the fact that claiming the cross-section of the cuttingteeth is critical to the main concept of the file and the fact that thisis a unique design not manufactured before.

In general, the sizes of the files are standard endodontics of 15-45,which is classified where the tip is at 0.15 mm, up to 0.45 mm at thetip.

In a preferred embodiment, the side facets of the saw teeth willconverge to an apex point, as opposed to converging to a linearextending cutting edge, extending between opposite upwardly extendingsides of the debriding cutting blade.

When used with motor drive, there will be a chuck for attaching it to amotor driven device, such as the W and H “Dental Werk” motor-driven bonecutting blade of Germany.

When in a motor driven embodiment, these new endodontic files may bepowered in an “up and down” jackhammer-type axial movement, alternatelyin a rotary movement, or in combinations thereof, by a motor drivenhandpiece. For example, these new manually operable endodontic files mayalternatively be powered in a mechanized motor driven embodiments,similar to a miniature jackhammer providing up and down axially alignedmovement or in a further motor driven mechanized embodiment, including arotary movement by a motor driven handpiece, or combinations of bothaxial up and down and rotary motions.

In summary, the endodontic re-treatment instrument includes a handle; adebriding section; a shank connecting the handle to said debridingsection; and the debriding section comprises a member with an upper edgehaving sharp saw tooth denticulated projections and a lowerblade-supporting portion.

The sharp saw tooth denticulated projections comprises two or more sidesextending up from the lower blade-supporting portion and converging to atop apex.

In various embodiments, the two or more sides of the sharp saw toothdenticulated projections are linear, converging to said apex, or arearcuate, forming a parabola, or are also arcuate, formed from adjacentinverse parabolas, where the arcuate sides converging to a pointed apex.

In another embodiment, each sharp saw tooth denticulated projectiontapers toward a linear extending top sharp cutting edge, and where eachsharp saw tooth denticulated projection extends side to side but withless of a width than said lower blade-supporting portion which extendsfrom the shank, so that the debriding section has a trapezoidal crosssection, wherein a top cutting edge is narrower than the wider, lowerblade-supporting portion, so that respective flat sides of the upperedge and the oblique lower blade-supporting portion are coterminous witheach other, extending slanting obliquely upward.

Alternately, in a preferred embodiment the linear converging sides ofthe sharp saw tooth denticulated projections converge to an apex cuttingpoint.

In a further embodiment, the sharp saw tooth denticulated projectionsare three-dimensional triangular profile pyramids.

Preferably, the debriding section tapers to a narrowed distal end, andthe shank and debriding section are orthogonal to its length. While theshank can be cylindrical, preferably the shank is cuboid in shape.

The distal end of the debriding section is ground to a sharp cuttingedge.

In another optional embodiment, the debriding section comprises a flatextended member with upper and lower edges, with the upper edge havingthe sharp saw tooth denticulated projections and concave curved valleysbetween respective sharp saw tooth denticulated projections.

The endodontic re-treatment instrument can have evenly high sharp sawtooth denticulated projections, or sharp saw tooth denticulatedprojections of variable levels, preferably with pointed tops.

While the triangular saw tooth denticulated projections are preferablylinear, optionally the projections can have curved sides formingprojections which are hyperbolic in shape.

In another embodiment, the debriding section includes a flat extendedmember with upper and lower edges having respective bi-level sharp sawtooth denticulated projections along both upper and lower edges.

The endodontic re-treatment instrument is preferably made of stainlesssteel, or nickel titanium, as well as from durable synthetic plasticmaterials.

The endodontic instrument is configured to be thin enough to cut intothe gutta percha material surrounding a carrier core in a treated rootcanal, as opposed to wider rotary instruments which because of theirincreased width can inadvertently contact the durable carrier core, andbe subject to torsional fatigue and/or breakage of the instrument or ofthe surrounding dentin.

In its thin configuration, the endodontic re-treatment instrumentincludes sharp saw tooth denticulated projections which are preferablyare triangular, having concave curved valleys therebetween, where theinstrument has a width of between 0.10 mm and 0.50 mm, a length ofbetween about 20 mm and 30 mm and a vertical height of between 0.40 mmand 0.75 mm, excluding a handle or motor driven adaptor at a proximalend thereof.

Preferably, the aforementioned endodontic instrument has a thin width ofabout 0.25 mm, a length of about 25 mm and a vertical height of about0.57 mm.

In a further alternate embodiment resembling a vegetable corer, theendodontic re-treatment instrument includes the shank and debridingsection being a straight, partially tubular member with a C-shaped crosssection orthogonal to its length, having spaced and facing paralleledges along a length thereof, and the spaced parallel edges along thedebriding section have the sharp saw tooth denticulated projectionsextending along at least a portion of said parallel edges of saidstraight partially tubular member with said C-shaped cross section.

Besides being handheld and manually operated, in the alternate motordriven embodiments, the endodontic re-treatment instrument furtherincludes an adaptor connectable to the shank for providing motor drivenstraight up and down, rotary in either direction, or alternate motionsof the debriding section.

The present invention also includes a method of clearing a root canal inpreparation for retreatment comprising the steps of:

-   -   a) inserting into said root canal an endodontic re-treatment        instrument comprising a handle, a debriding section, a shank        connecting the handle to the debriding section, where the        debriding section comprises a flat side with an upper edge        having sharp saw tooth denticulated projections along a side        opposite to said flat side, with each sharp saw tooth        denticulated projection extending upward; and    -   b) moving the instrument within the root canal for engaging a        gutta percha sleeve surrounding a central carrier core therein        until the carrier core is released from the root canal,        permitting its removal.

The method optionally a power unit mounted between the handle and theshank for providing straight up and down, rotary in either direction, oralternate motions of the debriding section.

Optionally the method includes clearing a root canal in preparation forretreatment where the shank and debriding section comprise a straight,partially tubular member with a C-shaped cross section orthogonal to itslength, having spaced and facing parallel edges along a length thereof,and the spaced parallel edges along the debriding section have the sharpsaw tooth denticulated projections extending from flat bases along thespaced parallel edges.

This optional step of using a vegetable corer type configuration canalso include a power unit mounted for providing straight up and down,rotary in either direction, or alternate motions of the debridingsection.

While the endodontic file of the present invention is primarily forendodontic retreatments of root canals, it can also be used fordebriding of damaged pulp and nerves in root canals being subject toinitial root canal treatments.

Normally the user does not need to use heat with the P-file, andsolvents might not be used since the design of the P-file teeth willnavigate areas that are unreachable with the rotary files and willprovide better cutting efficiency than the regular hand files in themarket (namely the K and H).

The endodontic file of the present invention with saw teeth denticulatedprojections serving as a cutting blade normally doesn't require theapplication of heat or solvent to breakaway or dissolve gutta perchaprior to removal of the central carrier core, but practitioners canelect to use either or both as adjuncts, since rotary instrumentsgenerally cannot be used solely for the re-treatment, but care needs tobe considered owing to the adverse side effects of heat and solventsdiscussed above.

Therefore, the cutting design configuration of the P-file of the presentinvention can help in reducing the need of using heat and/or solventsand thus avoiding their known adverse side effects.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention can best be understood in connection with theaccompanying drawings. It is noted that the invention is not limited tothe precise embodiments shown in the following drawings, in which:

FIG. 1 is a perspective view of a P-file of this invention.

FIG. 2 is a close-up detail perspective view of the P-file of FIG. 1,taken along circular view line “2” of FIG. 1, showing some cutting teethwhich each extend to a respective single point cutting pinnacle point,where the cutting blade is supported by and positioned adjacent to apreferably mainly cuboid shank support, which is insertable into ahandle.

FIG. 3A is a perspective detail view of a cutting blade teeth andsupport portions of triangular shaped saw teeth, which have planar sideswhich are co-terminus with the sides of the cutting blade supportportions, where the top cutting edges of the saw teeth extend linearly,but not as wide as the base of the support portions, where the saw teethand support portions are coterminous with each other and slanted upwardfrom a base which is wider than the apex of the saw teeth.

FIG. 3B is a top plan view of the cutting blade and blade supportportion of FIG. 3A.

FIG. 4A is a close-up perspective view of an alternate embodiment for anendodontic file with 3-D pyramidal shaped debriding teeth.

FIG. 4B is a top plan view of the endodontic file of FIG. 4A.

FIG. 5A is a side perspective view of a farther alternate embodiment fora “corer” endodontic file with pyramidal teeth on both file edges of ahollow half cylindrical two-sided cutting blade, having a hollow regionbetween the arcuate file cutting saw blade edges, forming a curved“C-shape” cross sectional configuration.

FIG. 5B is a close-up perspective view of the embodiment shown in FIG.5A, taken along circular view line “5B” of FIG. 5A.

FIG. 6 is a perspective view of a tooth being debrided using a P-file toremove the gutta-percha (GP) surrounding a central carrier core in aroot canal.

FIG. 7 is a perspective view of the result of the procedure of FIG. 6with the gutta percha (GP) broken down and the central carrier coreshown removed from the root canal.

FIG. 8A shows a design for file teeth with a curved valley extending inthe nadir between one tooth to an adjacent tooth.

FIG. 8B is a close-up detail side elevation of file teeth with a curvedvalleys shown in FIG. 8A.

FIG. 9 is a side elevation of the distal end of an endodontic filehaving all teeth at the same level.

FIG. 10 is a side elevation of the distal end of an endodontic filehaving teeth at different levels.

FIG. 11 is a side elevation of an endodontic file having hyperbolic,non-linear shaped cutting saw teeth.

FIG. 12 is a side elevation of an endodontic file having non-linearshaped cutting saw teeth, based upon inverse parabolas, but with apointed apex.

FIG. 13 is a side elevation showing an endodontic file with triangularteeth on both edges.

FIG. 14 is a side elevation view of another embodiment for an endodonticfile, showing critical dimensions.

FIG. 15 is a perspective view from below of the endodontic file of FIG.14, also showing critical dimensions.

FIG. 16 is a perspective view of a powered handpiece driving anendodontic file.

DETAILED DESCRIPTION OF THE DRAWINGS

FIGS. 1 and 2 illustrate two views of P-file 1 with handle 7, shank 5 onmetal portion, and a debriding cutting blade 3, with denticulatedprojections, such as pyramidal cutting teeth, which are preferably flatbut with triangular shaped profiles, when viewed in side elevationviews. The teeth of debriding cutting blade 3 are used for removing fromdebris within a tooth, such as pulp and nerve tissues in an originalendodontic root canal procedure or to remove gutta percha and debrisfrom a previously treated root canal, so that a centrally locatedcarrier core can be removed, without damage to its integrity, during there-treatment of the root canal.

FIGS. 1 and 2 show the preferred embodiment where the cutting teeth ofdebriding cutting blade 3, are shown bearing isosceles triangular shapesin profile, and where the teeth have a forward facing side face thatextends vertically, coterminous with the flat, also vertically extendingblade support member portion of the blade below the teeth. The pinnaclepoint of each tooth 3 of the cutting blade of the endodontic file 1 is asingle geometric point, as opposed to a linear extending cutting portionof FIGS. 3A and 3B, where in FIG. 2 the respective sides and rear of thesaw teeth converge at the pinnacle point. The shank 5, from which thecutting saw blade 3 extends, preferably has a cuboid cross section, withperpendicular sides and top and bottom, which is stronger to support thecutting blade 3 of sharp saw teeth. Cuboids such as shank 5 are convexpolyhedrons which have six faces with edges, where adjacent faces areperpendicular to other adjacent faces of the polyhedron.

In one alternate embodiment, FIGS. 3A and 3B the respective cuttingblade portion 3 has triangular-shaped saw teeth 3 a having sharp topedges 3 b, lower valley depth regions 3 c, flat side facets 3 d andlower blade support portions 3 e. The saw teeth 3 a's planar sides areco-terminus with the planar sides of the blade support portions 3 d,where the top cutting edges 3 b of the saw teeth 3 a extend linearly,but not as wide as the base of the blade support portion 3 e, where thesaw teeth 3 a and blade support portion 3 e are coterminous with eachother and slanted upward from a lower base of blade support portion 3 e,which is wider than the apexes 3 b of the saw teeth 3 a, so that in theview of FIG. 3A, the cross sectional end of the cutting blade portion 3is trapezoidal in shape. It is further noted that even when theendodontic cutting file of FIGS. 3A and 3B is very thin, the linearlyextending cutting edges 3 b of the saw teeth 3 a can present themselvesas almost pointed pinnacles, where each side of the cutting bladeportion 3 are separated from the other side by the tiny linearlyextending cutting edges 3 b of the saw teeth 3 a. Furthermore, while thecross sectional ends of the cutting blade portion 3 are shown astrapezoidal, they can also alternatively present themselves asvertically extending side edges of a cutting blade portion with sawteeth 3 a and top cutting edges 3 b.

The perspective detail view of another alternate embodiment for athree-dimensional endodontic file 11 in FIG. 4A shows an endodontic filewith shank 5 and a debriding section member 13 with three dimensional(3-D) pyramidal teeth 13 a tapering to a point 13 b. The teeth 13 a inthe form of 3-D pyramids emanate from a flat blade support base 13 c inforward debriding section member 13, are shown more clearly from abovein FIG. 4B. While FIGS. 4A and 4B show classical four-sided pyramidshapes for the cutting teeth 13 a, it is known that othernon-traditional pyramid shapes may be presented with three sides, ormore than four sides, emanating into a top pinnacle point 13 b.

The endodontic instrument 1 of FIGS. 1, 2, 3A and 3A, and the instrument11 of FIGS. 4A and 4B, can either have a handle for manual rotation andcutting by the endodontist, or can be attached to a power tool 41 in amotor driven version, such as shown in FIG. 16.

FIGS. 5A and 5B show a perspective view of a further alternateembodiment for a “corer” endodontic file 17 of this invention. The metalcutting section 19 is straight with a curved cross section orthogonal toits length. The top portion that is engaged with handle 7 is the shankwhich is also curved but has no cutting teeth. Pyramidal cutting teeth21, similar to teeth of the cutting blade 3 of the embodiment of FIGS.1-2, or of the teeth 3 a of the embodiment in FIGS. 3A and 3B, areformed on the axial edges of the forward section of metal cuttingsection 19. The distal end 23 of the cutting section 19 is ground to asharp cutting distal end. In use, file 17 is moved up and down androtated in clockwise or counterclockwise directions 25, in eitherdirection. The corer endodontic file 17 is therefore a straight,partially tubular member with a C-shaped cross section orthogonal to itslength, having spaced and facing parallel edges along at least a part ofa length of cutting section 19 and joined by the sharp distal end 23.The debriding section member includes sharp saw tooth denticulatedprojections 21 extending along at least a portion of the parallel edgesof the straight partially tubular member 19, with the C-shaped crosssection. The extended C-shaped endodontic instrument 17 of FIGS. 5A and5B, can either have a handle for manual rotation and cutting by theendodontist, or can be attached to a power tool in a motor drivenversion, such as power tool 41 of FIG. 16.

Furthermore, FIGS. 6 and 7 illustrate some of the method involved indebridement as part of the retreatment process. In FIGS. 6 and 7, apartial tooth 33 with a side sliced to reveal three root canals belowthe gum 31 line, is shown. FIG. 6 shows a P-file 1 reciprocating whileengaged with the obturating gutta percha (GP) annular seal 36 around theedge of plastic carrier core 35. The objective is to free root canal 39of the obturating gutta percha 36 and plastic carrier core 35 as shownin FIG. 7. Therefore, the main goal of the endodontist in re-treatingthis kind of obturation material in the carrier core 35 (carrier-basedobturation materials) is to maintain the carrier 35 as intact aspossible, for easy retrieval, by indirectly digging into and removingthe gutta percha material 36 surrounding the carrier 35 with theendodontic files 1, 11 or 17 of the present invention, without causingtorsional fatigue and possible damage with a wide rotating instrument,but without the complexities of re-treatment with rotary files. By usingthe thin saw-blade teeth and thin cross-section of the cutting part, theendodontic files 1, 11 or 17 can fit and dig into the confines of thegutta percha 36 located between the carrier 35 and the dentin wall oftooth 33, while ripping through the surrounding gutta-percha 36 withoutpotentially damaging the carrier 35, which is something the prior artrotary files cannot do without difficulty, owing to their wider, roundedcross-section and break susceptible rotary fluting.

FIGS. 8A, 8B, 9, 10, 11, 12 and 13 show alternate embodiments fordifferent geometric shapes for the saw teeth denticulated projections.

For example, FIG. 8A shows an enlarged design for an endodontic filehaving triangular teeth 50 with a concave curved valley 52 located atthe nadir between adjacent teeth 50. The actual file teeth of FIG. 8Aare shown in FIG. 8B as teeth 54, also with concave curved valleys 52located at the nadirs between adjacent teeth 54.

In the embodiment of FIG. 9, the distal end 56 of an endodontic file(enlarged) with evenly high teeth 58 are shown, which are not equalsided isosceles triangles.

In the embodiment of FIG. 10, the enlarged distal end 60 of anendodontic file having teeth of variable levels 62 is shown.

FIG. 11 shows an endodontic file tooth profile in which saw teethdenticulated projections 64 are hyperbolic in shape. In this embodiment,the endodontic file can optionally have parabolic-shaped saw teeth 64adjacent to one another, where instead of linear sides extending upwardtowards an apex point, as in FIGS. 1-5 and 8-10, the sides of saw teeth64 would be extending upward and converging in curved lines towards atangent to a curve, as in a parabola.

FIG. 12 shows an endodontic file tooth profile, similar to FIG. 11 inwhich saw teeth 64 are hyperbolic in shape. But in FIG. 12, theendodontic file can optionally have curved, arcuate-shaped saw teethdenticulated projections 64 a adjacent to one another, where the curvedarcuate sides extending upward towards an apex point 64 b. Therefore,the sides of saw teeth 64 a would be extending upward and convergingtowards a sharp apex point 64 b. While the saw teeth in FIG. 11 form aparabola, in FIG. 12 the sides of each saw teeth are one half of adownwardly extending parabola, so that the curved sides meet at apointed apex.

Therefore, in general, the saw teeth comprise two or more sidesconverging to a top apex point or region. When the converging sides arelinear converging to an apex, as in FIGS. 1-4B and 8A-10, the shape ofeach saw tooth is that of a triangle, either equilateral ornon-equilateral. If the converging sides are curved and arcuate,converging to a curved or pointed apex, as in FIGS. 11 and 12, then theshape of each saw tooth 64 and 64 a of the blade is that of a parabola,as in FIG. 11, or of adjacent sides of an inverse parabola, as in FIG.12.

FIG. 13 shows an embodiment for a double-sided cutting endodontic file66 having triangular teeth 68 on both edges.

FIGS. 14 and 15 illustrate two views of an endodontic file 71 (withhandle not shown), cuboid shaped shank 75 on a metal portion, andcutting blade 73 having triangular cutting teeth 74 bearing isoscelestriangular shapes in profile, where the teeth 74 have a forward facingside face that extends vertically, coterminous with the flat, alsovertically extending shank support portion of the blade 73 below theteeth 74. Each tooth 74 of the cutting blade 73 of the endodontic file71 has a sharp cutting point or region 74 a. The shank 75 has a cuboidcross section. FIG. 14 also shows the endodontic file 71 havingtriangular teeth 74, but with a curved concave valley 74 b betweenadjacent triangular teeth 74. Concave valley 74 b is equivalent to theconcave valley is identified as reference numeral “52” in drawing FIGS.8A and 8B.

While dimensions may vary, in a preferred embodiment shown in FIGS. 14and 15, the linear measurements are shown therein in millimeters,Therefore the length of endodontic file 71 is about 25 mm (0.984 inches)and the height at the proximal rear edge is about 0.57 mm. Additionally,the length of the cuboid shank 75 is about 9 to 9.33 mm, leaving theblade length of cutting blade 73 to be about 15.67 to 16 mm. The54.66-degree angle shown in FIG. 14 refers to the angle between the lastsloping edge of the saw teeth 74, as against the beginning front edge ofthe shank 75. The angle of 169.82 degrees, located at the distal cuttingedge, refers to the angle from the horizontal bottom of cutting blade 73to the initial slope of the distal portion 73 a, before the first of thecutting teeth 74. The 79.14 degree angle represents the angle of thevalley between a saw tooth 74 and its next adjacent saw tooth 74.

The number “R0.09” refer to length in millimeters of the radius of thesmall concave portion 74 b in the depth of the respective valleysbetween each successive triangular silhouette shaped saw teeth 74.

The endodontic re-treatment instrument 71, is shown in an alternateembodiment, with sharp saw tooth denticulated projections 74, which aretriangular in shape, having concave curved valleys 74 b therebetween.The re-treatment instrument 71, can have a width extending in a range ofbetween 0.10 mm and 0.50 mm, a length extending in a range of betweenabout 20 mm and 30 mm and a vertical height extending in a range ofbetween 0.40 mm and 0.75 mm, excluding a handle or motor driven adaptorat a proximal end thereof.

While dimensions may vary, because the example shown in FIGS. 14 and 15has a width of only between 0.10 mm and 0.50 mm, preferably about 0.25mm, along its length, it can easily dig into the three areas of guttapercha thicknesses described previously in Alhashimi et al, where thethicknesses of 0.376, 0.357 and 0.591 provide ample room for insertionof the endodontic file of FIGS. 14 and 15 with its thin thicknesspreferably of only 0.25 mm, or within the range of between 0.10 mm and0.50 mm. While it would be too thick to be inserted at the gutta perchathickness of only 0.164, removal of three quarters of the gutta perchaat the thicker thickness of 0.376 mm, 0.357 mm and 0.591 mm will enablethe thinnest part to crumble by removal of its adjacent thicker portionsexceeding the preferable 0.25 mm thickness of the endodontic file shownin FIGS. 14 and 15.

Generally, the deepest any endodontic re-treatment file tool can reachinside the root canal being re-treated is the best. For endodonticinstrument with saw tooth denticulated cutting projections, of thepresent invention, reaching just halfway will be enough (average of 8-10mm) to dig into and breakup the gutta percha to be removed from a toothroot canal of approximately 16-20 mm in length. However, in certaincircumstances where the canal is straight, as opposed to curved at theapical end, yet, it can get into the full length of the canal owing toits design and thickness.

While the aforementioned new endodontic files introduced by thisinvention have been shown with handles for manual use, they can bepowered. FIG. 16 shows a powered handpiece 41 comprising handpiecehandle 43, power unit 45, and one of the three files of this invention(minus handles) chucked in power unit 45. The power unit can have thecapability to follow the motions indicated by arrows 47, straight up anddown, rotary in either direction, or alternate circular motion.

A preferred embodiment for a motor driven handpiece uses the prior artmotor driven apparatuses of W & H DentalWerks of Germany for cutting jawbones may be adapted for orthodontic rework. Their S-8 series supportssagittal, oscillating, or reciprocating movement.

For example, while the three new endodontic files introduced by thisinvention have been shown with handles for manual use, they can bepowered. FIG. 16 shows a powered handpiece 41 comprising handpiecehandle 43, power unit 45, and one of the various files of this invention(minus handles) chucked in power unit 45, The power unit can have thecapability to follow the motions indicated by arrows 47, axiallystraight up and down, rotary in either direction, alternate circularmotion, or combinations thereof.

Although the aforementioned U.S. Pat. No. 4,353,698 of McSpadden citedabove is for use in obturating stripped root canals and not debridement,similar powered rotary tools with similar working ends are used indebridement today. With the use of plastic carriers surrounded by guttapercha (GP) or similar obturating material in a root canal undergoingretreatment, debridement including removal of the plastic carrier moreoften results in unwinding and separation of retreatment files(ProTaper). Two retreatment files of this invention may be better suitedas powered working ends. One version is the generally thin P-file 1 ofFIGS. 1 and 2, 3A and 3B, the P-file 11 of FIGS. 4A, 4B, the doublesided file of FIG. 13, or the file 71 of FIGS. 14 and 15. Anotherversion is the “corer file” of FIGS. 5A and 5B when sized with a crosssection inner radius slightly larger than the outside diameter of theplastic carrier. These files would be moved in a compound fashion,reciprocating for active cutting away gutta percha, while rotatingslowly (or in small discrete steps) around the carrier core for removalwithout damage by pulling from above with an instrument, such as atweezer or other grasping hand tool. The instrument's path followedwould be similar to that illustrated in FIG. 6, for removal of the outergutta percha sheath 36 and central carrier core 35 The carrier core 35is removed from root 39 intact, without damage to carrier core 34, asshown in FIG. 7.

In the foregoing description, certain terms and visual depictions areused to illustrate the preferred embodiment. However, no unnecessarylimitations are to be construed by the terms used or illustrationsdepicted, beyond what is shown in the prior art, since the terms andillustrations are exemplary only, and are not meant to limit the scopeof the present invention.

It is further known that other modifications may be made to the presentinvention, without departing the scope of the invention, as noted in theappended Claims.

I claim:
 1. A dental instrument comprising: a debriding section forendodontic re-treatment; a handle adapted for manually rotating saiddebriding section and cutting, said instrument being unpowered; a shankdirectly connecting said handle to said debriding section; saiddebriding section comprising a flat planar member cutting blade in withonly an upper edge thereof having sharp saw tooth denticulatedprojections and a lower blade supporting portion comprising a straightedge; and said saw tooth denticulated projections comprising isoscelestriangular shaped teeth in profile, and where each said tooth has aforward facing side edge that extends at a vertical angle from saidlower straight edge.
 2. The dental instrument as in claim 1 furthercomprising each said sharp saw tooth denticulated projection comprisestwo or more sides extending up from said lower blade-supporting portionand converging to a top apex.
 3. The dental instrument as in claim 2wherein said two or more sides of said sharp saw tooth denticulatedprojections are linear, converging to said apex.
 4. The dentalinstrument as in claim 3 wherein said linear converging sides of saidsharp saw tooth denticulated projections converge to an apex cuttingpoint.
 5. The dental instrument of claim 3 in which said sharp saw toothdenticulated projections have pointed tops.
 6. The dental instrument ofclaim 1 in which said debriding section tapers to a narrowed distal end.7. The dental instrument as in claim 1 wherein said shank and debridingsection are orthogonal to its length.
 8. The dental instrument of claim7 in which a distal end of said debriding section is ground to a sharpcutting edge.
 9. The dental instrument as in claim 1 wherein said shankis cuboid in shape.
 10. The dental instrument of claim 1 having evenlyhigh sharp saw tooth denticulated projections.
 11. The dental instrumentof claim 1 having said sharp saw tooth denticulated projections ofvariable levels.
 12. The dental instrument as in claim 1 wherein saidinstrument is made of stainless steel.
 13. The dental instrument as inclaim 1 wherein said instrument is made of nickel titanium.
 14. Thedental instrument as in claim 1 wherein said sharp saw toothdenticulated projections are triangular, have concave valleystherebetween, said instrument having a width of between 0.10 mm and 0.50mm, a length of between about 20 mm and 30 mm and a vertical height ofbetween 0.40 mm and 0.75 mm, excluding a handle or motor driven adaptorat a proximal end thereof.
 15. The dental endodontic re treatmentinstruction as in claim 1 wherein said sharp saw tooth denticulatedprojections are triangular, have a concave valley therebetween, saidinstrument having a width of about 0.25 mm, a length of about 25 mm anda vertical height of about 0.57 mm.
 16. A dental instrument consistingof: a debriding section for endodontic re-treatment; a handle adaptedfor manually rotating said debriding section and cutting, saidinstrument being unpowered; said debriding section comprising astraight, partially tubular member with a C-shaped cross sectionorthogonal to its length, having spaced and facing parallel edges alonga length thereof and joined by a sharp distal end, and said debridingsection having sharp saw tooth denticulated projections extending alongat least a first portion of said parallel edges of said straightpartially tubular member with said C-shaped cross section, and a secondportion of said debriding section adjacent said sharp distal edge beingfree of said denticulated projections.
 17. The dental instrument as inclaim 16 further comprising a shank supporting said debriding section,said shank being a straight partially tubular member with a C-shapedcross section orthogonal to its length, and a third portion of saiddebriding section adjacent said shank also being free of saiddenticulated projections.
 18. The dental instrument as in claim 16wherein said distal end further includes sharp saw tooth denticulatedprojections.
 19. A dental instrument comprising: a debriding section forendodontic re-treatment; a handle adapted for manually rotating saiddebriding section and cutting; a shank directly connecting said handleto said debriding section; said debriding section comprising anelongated flat planar member with only an upper edge having sharp sawtooth denticulated projections and a lower opposite facing edgecomprising a flat surface; said sharp saw tooth denticulated projectionscomprising triangular-shaped saw teeth having sharp top edges, lowervalley depth regions, and flat side facets, said flat side facetssloping inwardly from said lower edge up to said sharp top edges of saidteeth; and whereby said sharp top edges of said saw teeth are not aswide as said lower valley depth regions, ends of said sharp top edgesnot extending out as far as said lower depth regions extend.